Is Fault-Tolerant Quantum Computation Really Possible?

TL;DR

This paper critically examines the feasibility of fault-tolerant quantum computation by analyzing the threshold theorem and its assumptions, raising doubts about large-scale quantum computing's practicality due to idealized elements in the theory.

Contribution

It provides a critical analysis of the threshold theorem, questioning its physical realism and implications for large-scale fault-tolerant quantum computation.

Findings

Mathematics behind the threshold theorem may be detached from physical reality

Ideal elements are always present in the fault-tolerance constructions

Serious doubts about large-scale quantum computation feasibility

Abstract

The so-called "threshold" theorem says that, once the error rate per qubit per gate is below a certain value, indefinitely long quantum computation becomes feasible, even if all of the qubits involved are subject to relaxation processes, and all the manipulations with qubits are not exact. The purpose of this article, intended for physicists, is to outline the ideas of quantum error correction and to take a look at the proposed technical instruction for fault-tolerant quantum computation. It seems that the mathematics behind the threshold theorem is somewhat detached from the physical reality, and that some ideal elements are always present in the construction. This raises serious doubts about the possibility of large scale quantum computations, even as a matter of principle.